Amphoacetates are a well known group of surfactants (see U.S. Pat. No. 5,744,063, DE 36 39 752, DE 196 36 205, DE 43 07 709 and DE 42 40 154). These amphoacetates are made by reacting 1-hydroxyethyl-2-alkyl-2-imidazoline with chloroacetic acid or the alkali salt thereof. This reaction, however, does not yield a single product but a ring-opening of the imidazoline yields a mixture of the secondary monoamide and the tertiary monoamide of the formulae EQU RCONH--CH.sub.2 CH.sub.2 --NH--CH.sub.2 CH.sub.2 --OH
and ##STR3##
Subsequent reaction with chloroacetic acid or chloroacetate yields the corresponding mixture of secondary and tertiary amphoacetates. These mixtures of amphoacetates, however, have a decisive drawback in that the viscosity of aqueous solutions of such mixtures of amphoacetates increases upon storage.
Thus the problem was to make amphoacetates which avoid such increase in viscosity. Based on kinetic investigations into the hydrolysis of the imidazoline starting product by means of NMR spectroscopy it has been found that under the conditions as stated below predominantly secondary amphoacetates can be produced, the aqueous solutions thereof retain their low viscosity even upon prolonged storage.